Thanks again for all the feedback, everyone. It's very gratifying to be at a point where I can post some solid data, rather than the typical speculation that normally accompanies HP figures.

Geoff: I'll be glad to post some mileage figures in a few weeks, after I get tired of hitting the gas pedal every chance I get. Right now, it seems I can get at least 18 mpg on the highway if I can keep my foot out of it. I have it tuned pretty rich at WOT to keep detonation in check, so full throttle escapades definitely use a lot of fuel, but believe it or not, we tuned the rest of the fuel table for economy. My cruising AFR, for example, is between 13.9:1 and 14.6:1, as you can see here:



Look at the left axis, which is manifold pressure (as measured in kPa, or kilo pascals). Everything below 100 kPa is vacuum, so cruising at 70 mph in 5th gear @ 3500 rpm, my air fuel ratio is a solid (and reasonably efficient) 13.9:1. If i drop down to 65 mph, the AFR rises to 14.6:1, or near stoich, which is right where you'd want it to be for economy.

The key is keeping my foot out of it, which is kinda hard at the moment <img src="/forums/images/graemlins/smile.gif" alt="" /> Look at the rest of the table: as pressure and RPMs rise, so does fuel consumption. At wide open throttle and peak boost, we're throwing a hell of a lot of fuel into the cylinder to keep it from detonating (thanks to California's lousy 91 octane gasoline...). If I go with water injection (just as a "what it...") I can achieve the same effect at WOT by replacing a lot of that extra fuel with water vapor. I'm not sure I want to do that, but it is intriguing.

-Jeff